1. Field of the Invention
The invention relates to a cooling system for cooling the stator and/or the rotor of a generator, and to a method for cooling the stator and/or the rotor of a generator.
A hydrogen-cooled synchronous generator with a water-cooled stator winding is described in the book "Synchronmaschinen" [Synchronous Machines], AEG Telefunken Handbucher, Volume 12, Berlin 1970, on page 53. Generators with a water-cooled stator winding require a water loop. It comprises pumps for circulating the primary cooling water, return coolers and filters which ensure that the stator winding is not soiled, and an expansion vessel which is fitted on top on the machine. Fine filters and an ion exchanger for preparing the water are connected in the shunt circuit to this main circuit. Since the cooling water must be fed to the stator winding via insulating hoses, a small fraction of hydrogen can diffuse via them from the machine interior into the water circuit. This hydrogen fraction is given the opportunity of degassing from the water in the not entirely filled expansion vessel. It is led to the outside via a pressure control valve and a gas meter.
German patent application DE 22 22 487 describes a device for removing non-absorbed gases in liquids in the case of liquid-filled electric machines. In accordance with FIGS. 1 and 2 of that document, two concepts are applied for a cooling circuit. On the one hand, a coolant compensating container via which coolant is supplemented is connected to the cooling circuit via a spur line. In that compensating container which is disposed outside of the cooling circuit, a degassing container through which the entire coolant flow passes is connected into the cooling circuit. Outgassing of the coolant occurs in the degassing container. The gases are discharged to the outside. In accordance with the other concept, the compensating container for the coolant is integrated into a shunt circuit connected in parallel with the main cooling circuit. In this case, a smaller coolant flow of the shunt circuit passes continuously through the compensating container which serves simultaneously as a degassing container.
A cooling water circuit for a water-cooled electric machine is described with the aid of FIG. 5 in Siemens-Zeitschrift [Siemens Journal], Vol. 41, 1967, issue 10, pages 838-39. The cooling water must have a low electric conductivity for reasons of insulation. For this reason, chemical filters or ion exchangers, which continuously reduce the ion concentration in the cooling water, are connected into the cooling circuit.